1. Field of the Invention
The present invention relates generally to a portable information radio terminal device or a personal digital assistance (PDA) and a manufacturing method thereof. More particularly, the invention relates to a portable information radio terminal device and a manufacturing method thereof, which can effectively prevent peeling off, breakage or so forth of an electrical connecting portion of an electronic part mounted on a printed circuit board in a device casing.
2. Description of the Related Art
Conventionally, as shown in FIGS. 3A and 3B, a printed board 12 incorporated in a portable information radio terminal device 11 is secured in a device casing by screws 15 and bosses 17. Accordingly, when an impact is exerted on the portable information radio terminal device 11, portions of the printed circuit board 12 secured by the screws cannot vibrate or deflect in response to the impact, which thereby causes stress to concentrate about the portions secured by the screws to amplify the vibration or deflection of the printed board 12. As a result, peeling can be caused in a solder ball (electrical connecting portion) of a chip size package (CSP) mounted on the printed board 12.
In Japanese Unexamined Utility Model Publication No. Showa 58-162689, the following technology has been disclosed. Disclosed in the above-identified publication is a printed board support structure of an electronic equipment, in which a printed board mounting a printed wiring and various parts, such as relays and so forth, is rigidly fixed in a casing. Elastic engaging projections are projected from a printed board mounting surface of the casing. Also, auxiliary projections are projected in opposition to the elastic engaging projections across the printed board with a distance. In the printed board, engaging holes to engage with the engaging projections are formed for forming the supporting structure of the printed board of the electronic equipment. On the other hand, between each of the supporting portions of the casing and the printed board, elastic member, such as rubber member is disposed with a space portion for accommodating tolerance.
On the other hand, in Japanese Unexamined Patent Publication No. Heisei 8-23181, the following technology has been disclosed. A circuit board has a structure to be tightly clamped by first and second rollers. When the circuit board is inserted between the first and second rollers, the first and second rollers are rotated in a board inserting direction by a frictional force. With such construction, vibrations caused in the equipment casing are absorbed to protect the circuit board from vibration. Furthermore, the circuit board can be smoothly inserted into the casing.
It is desirable to maintain electrical connection of the electronic parts mounted on the board in the device body when the portable information radio terminal device is subject to an impact (external force) due to the device being dropped or so forth. It is also desired that large vibrations and/or impact not be transmitted to the electronic parts within the device body to maintain electrical connection of the electronic parts and to thus not be a cause of failure of the electronic parts.
Also, it is desired to be able to easily produce the portable information radio terminal device to be resistant against such an impact as set forth above.